1. Field of the Invention
The present invention relates to a power off sequence of an image forming apparatus.
2. Description of the Related Art
A situation can occur in which, when supply of power to a hard disk is interrupted during the storage of data in a storage medium such as a hard disk, part of the data is not written into the hard disk and is thus lost. Japanese Patent Laid-Open No. 2005-267370 proposes a timer circuit for continuing to supply power for a predetermined period of time even if the user turns off the power switch. According to Japanese Patent Laid-Open No. 2005-267370, data can be protected because the supply of power continues until the hard disk drive finishes data processing.
Most image forming apparatus include two different control units (a system control unit and a printer control unit). In addition, the system control unit and the printer control unit each include a CPU. The CPU of the system control unit performs, for example, overall control of the entire image forming apparatus. The CPU of the printer control unit controls a printer engine. When the CPU of the system control unit transmits a shutdown instruction, the CPU of the printer control unit receives the shutdown instruction, and shuts down various loads controlled by the printer control unit. In the case where, for example, paper is being conveyed, the printer control unit checks the discharge of paper, and stops the power supply from the power unit. In order to safely shut down the image forming apparatus, the operator inputs a shutdown instruction through an operation unit. The shutdown instruction is generated by, for example, the operator pressing a predetermined switch provided in the operation unit, and the instruction is notified to the system control unit.
However, if an anomaly occurs in the system control unit, even when the operator issues a shutdown instruction to the system control unit, the shutdown instruction is not transmitted to the printer control unit. As a result, the printer control unit cannot perform a normal shutdown. Japanese Patent Laid-Open No. 2005-267370 does not give consideration to this issue.